Sensing transducer using a Schottky junction and having an increased output signal voltage

Abstract

A sensing transducer (10,30) and a method therefor uses a Schottky junction (12) having a conductive layer (16) disposed on a semiconductor substrate (14). The conductive layer (16) is generally formed from the reaction of a metal with a portion of the semiconductor substrate (14). One example of the conductive layer (16) is a metal silicide layer. In one pressure sensing approach, a substantially constant reverse current (I 1 ) is applied to the Schottky junction (12). The change in reverse output voltage of the junction (12) is proportional to the change in pressure on the junction (12) itself, and can thus be used to sense pressure. This output voltage change is significantly higher than that achieved with prior pressure transducers and permits the output signal of the transducer (10,30) according to the present invention to be substantially used without extra amplification or other conditioning.

We claim: 
     
       1. A sensing transducer, comprising: a semiconductor substrate;   a conductive layer disposed on said semiconductor substrate to provide a Schottky junction that is responsive to a substantially uniform pressure on said conductive layer, wherein said conductive layer is a compound formed by a reaction of a metal and a portion of said semiconductor substrate; and   a contact coupled to said conductive layer.   
     
     
       2. The transducer of claim 1 wherein said semiconductor substrate is a compound semiconductor. 
     
     
       3. The transducer of claim 1 wherein said semiconductor substrate is silicon. 
     
     
       4. The transducer of claim 1 wherein said metal comprises at least one member of a group consisting of a refractory metal and a near-noble metal. 
     
     
       5. The transducer of claim 1 wherein said metal comprises at least one member of a group consisting of platinum, palladium, tungsten, and titanium. 
     
     
       6. The transducer of claim 1 wherein said Schottky junction has a reverse bias characteristic responsive to said pressure. 
     
     
       7. The transducer of claim 1 wherein said conductive layer has a top surface and said pressure is applied to said top surface. 
     
     
       8. The transducer of claim 1 wherein a change in a reverse bias current-voltage characteristic of said Schottky junction corresponds to an output signal from said pressure transducer and is proportional to a change in said pressure. 
     
     
       9. The transducer of claim 1 wherein said semiconductor substrate is polysilicon. 
     
     
       10. The transducer of claim 1 wherein said semiconductor substrate is an epitaxial layer. 
     
     
       11. The transducer of claim 1 wherein said semiconductor substrate has a substantially single-crystalline structure and is doped with an n-type dopant. 
     
     
       12. The transducer of claim 1 further comprising a guard ring disposed proximate to an edge of said Schottky junction. 
     
     
       13. The transducer of claim 1 further comprising a first n-type region underlying said conductive layer, wherein said semiconductor substrate is n-type and said first n-type region has a dopant concentration greater than said semiconductor substrate. 
     
     
       14. The transducer of claim 13 wherein: said contact has a first edge and a second edge; and   said first n-type region extends at least from said first edge to said second edge of said contact.   
     
     
       15. A sensing transducer, comprising: an n-type silicon substrate;   a metal silicide layer disposed on said n-type silicon substrate to provide a Schottky junction that is responsive to a pressure on said Schottky junction, wherein a change in a reverse bias current-voltage characteristic of said Schottky junction corresponds to an output signal from said sensing transducer and is proportional to a change in said pressure; and   a contact coupled to said metal silicide layer.   
     
     
       16. The transducer of claim 15 wherein said metal silicide layer comprises at least one member of a group consisting of platinum, palladium, tungsten, and titanium. 
     
     
       17. The transducer of claim 16 wherein said n-type silicon substrate has a dopant concentration of about 1×10 16  atoms/cm 3 . 
     
     
       18. A method for sensing pressure, comprising the steps of: applying a pressure to a Schottky junction wherein said Schottky junction comprises a conductive layer disposed on a semiconductor substrate, said conductive layer being a compound formed by a reaction of a metal and a portion of said semiconductor substrate; and   generating an electrical signal that is responsive to said pressure, wherein said electrical signal has a magnitude that is a function of said pressure and wherein said electrical signal corresponds to a reverse bias characteristic of said Schottky junction.   
     
     
       19. The method of claim 18 wherein said electrical signal is proportional to said pressure. 
     
     
       20. The method of claim 19 wherein said step of generating an electrical signal comprises applying a substantially constant reverse current to said Schottky junction. 
     
     
       21. The method of claim 18 wherein said electrical signal is a change in output voltage greater than about 3 V for a reverse bias current applied to said Schottky junction of greater than about 300 micro-amps.